writer.append("The World Wide Web", 4, 9);
    writer.append("!");

    assertEquals("Hello, World!", builder.toString());
  }

  public void testCloseFlush() throws IOException {
    SpyAppendable spy = new SpyAppendable();
    Writer writer = new AppendableWriter(spy);

    writer.write("Hello");
    assertFalse(spy.flushed);
    assertFalse(spy.closed);

    writer.flush();
    assertTrue(spy.flushed);